diff -Naur old/picard/webservice.py new/picard/webservice.py
--- old/picard/webservice.py	2011-10-23 19:15:29.000000000 +0200
+++ new/picard/webservice.py	2012-04-28 17:43:17.562422696 +0200
@@ -149,8 +149,11 @@
             url.setPassword(self.config.setting["password"])
         request = QtNetwork.QNetworkRequest(url)
         request.setRawHeader("User-Agent", "MusicBrainz-Picard/%s" % version_string)
-        if method == "POST" and host == self.config.setting["server_host"]:
-            request.setHeader(QtNetwork.QNetworkRequest.ContentTypeHeader, "application/xml; charset=utf-8")
+        if data is not None:
+            if method == "POST" and host == self.config.setting["server_host"]:
+                request.setHeader(QtNetwork.QNetworkRequest.ContentTypeHeader, "application/xml; charset=utf-8")
+            else:
+                request.setHeader(QtNetwork.QNetworkRequest.ContentTypeHeader, "application/x-www-form-urlencoded")
         send = self._request_methods[method]
         reply = send(request, data) if data is not None else send(request)
         key = (host, port)
@@ -370,6 +373,7 @@
     def _encode_acoustid_args(self, args):
         filters = []
         args['client'] = ACOUSTID_KEY
+        args['clientversion'] = version_string
         args['format'] = 'xml'
         for name, value in args.items():
             value = str(QUrl.toPercentEncoding(value))